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The freezing point of benzene decreases by 0.45 ° C on adding 0 . 2 g of acetic acid to 20 g of benzene. If acetic acid associates to form a dimer in benzene, then what is the percentage association of acetic acid in benzene? K f for benzene = 5 .12 K kg mol - 1

Options

  1. A80 . 4 %
  2. B74 . 6 %
  3. C94 . 6 %
  4. D64 . 6 %

Correct answer

C. 94 . 6 %

Step-by-step solution

2 CH 3 COOH ⇌ CH 3 COOH 2 1 - α α 2 i = 1 - α 2 ΔT f = i × K f × m 0 .45 = i × 5 .12 × 0 .2 × 1000 60 × 20 i = 0 .527 = 1 - α 2   ⇒ α = 0 .946 or 94 . 6 %

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